The present invention refers to a cutting insert as well as a holder for metal cutting machining. More exactly the invention concerns a tool which enables the clamping of indexible inserts with different geometrical shapes in one and the same insert pocket.
The use of detachable, indexible inserts is nowadays accepted practice within more or less the entire field of metal cutting machining, i.e. within both turning, milling, drilling, etc. They are usually manufactured in coated or uncoated cemented carbide, but also certain ceramic materials can be used. These different indexible inserts may have very varying geometrical basic shapes, depending on cutting economy and application. They can, for example, be triangular, rhombic, square, rectangular, round, hexagonal (including so-called trigon inserts) and octagonal.
Common for all the different conceivable insert shapes is that they require an insert pocket in the holder adapted to each specific shape. Consequently a square cutting insert normally requires an insert pocket with two support or abutment surfaces which are at right angles to each other; a triangular cutting insert requires generally two abutment surfaces which are angled 60xc2x0 to each other, etc. This means that a change of insert shape also craves a change of holder. This is both time consuming and expensive. Further the designer""s freedom of choice when designing a new cutting insert is limited, since the outer contour of the cutting insert must function at least partially as an operational cutting edge and clearance surface, and also as an abutment surface, when the surface in question is indexed in against the actual insert pocket. This makes it impossible to provide certain desirable cutting geometries. Should the designer nevertheless wish to use such a cutting geometry, he/she will be forced to resort to an insert design without an operational cutting geometry on the side of the cutting insert facing the insert pocket.
A first aim with the present invention is consequently to create cutting inserts which can be clamped in one and the same insert pocket despite having different contour lines.
Another aim with the invention is to produce a cutting insert which does not need to have its side surfaces abut against any abutment surfaces of the holder.
Still a further purpose with the present invention is to produce an insert pocket having wider manufacturing tolerances.
Cutting inserts with a recess in the bottom surface of the cutting insert are known previously through Carlsson et al. U.S. Pat. No. 4,674,924. In that case, the recess functions in its entirety (also even its three side surfaces) as pure non-contact surfaces, whereby the cutting insert shall abut on its three corner parts, which furthermore most preferably are to be angled upwards and inwards.
The present invention involves a tool for metal cutting machining. The tool comprises a holder arrangement, an indexible cutting insert, and an insert-securing device. The holder arrangement includes an insert-receiving site for receiving a cutting insert. The site includes an upwardly facing bottom support surface and at least two generally upright support surfaces disposed in non-parallel relationship. The cutting insert is seated on the site and includes an upwardly facing chip surface, a downwardly facing abutment surface, and a side surface structure intersecting the chip surface to form therewith a cutting edge structure. The side surface structure defines an outer perimeter of the insert. The generally downwardly facing abutment surface is disposed inside of the outer perimeter and abuts the bottom support surface of the site. The insert further includes at least three generally upright abutment surfaces disposed inside of the outer perimeter. At least two of the generally upright abutment surfaces are disposed in facing relationship to respective ones of the generally upright support surfaces. The insert-securing device is arranged for generating a first force oriented substantially perpendicular to a plane of the insert which presses the downwardly facing abutment surface against the upwardly facing support surface, and a second force oriented substantially parallel to the plane of the insert which presses at least two, but less than all, of the generally upright abutment surfaces against respective ones of the generally upright support surfaces. The second force extends at an oblique angle to the at least two generally upright abutment surfaces. The insert is indexible to bring another portion of the cutting edge arrangement into active cutting position. The generally upright abutment surfaces are arranged such that in response to indexing of the cutting insert, one of the generally upright abutment surfaces previously disposed out of engagement with a generally upright support surface is moved into abutment with a generally upright support surface, and a generally upright abutment surface previously in abutment with a generally upright support surface is moved out of abutment with all of the generally upright support surfaces.